1. Field of the Invention
This invention relates in general to storage systems, and particularly to, systems for backing up storage volumes in a storage system.
2. Description of the Related Art
Mirroring storage volumes stored on a production side to a back-up site is well known in the art. When storage volumes are mirrored, the storage volumes stored on a primary side are transmitted to the back-up side where the storage volumes are then stored on one or more virtual storage tape servers (VTS). The back-up side is used to recover data in the event of a disaster on the primary side or is used when there is maintenance being performed on the primary side.
When a particular storage volume stored on a VTS needs to be accessed by a host residing on the back-up site, the VTS first looks to see if the storage volume is stored in its cache. If the storage volume is in the cache, the storage volume can be quickly retrieved from the cache and transmitted to the host. If the storage volume is not in cache, the storage volume must be retrieved from the storage tape of the VTS prior to transmitting the storage volume to the host, which is much slower than retrieving the storage volume from the cache.